Piston pump



- April 8, 1941. M. ROEDEL I PISTON PUMP Filed Nov. 15, 1938 m /A I l A Apr. 8, 1941 PISTON PUMP Max Roedel, Munich, Germany, assignor to F. X. Meiller, Maschinenfabrik & Wagenbauanstalt,

Munich, Germany r I Application November 15. 1938, Serial No. 240,542

In Germany October 12, 1937 5 Claims.

This invention relates to a piston pump with a piston having an axial bore in its head and of cup-shape, through which the liquid flows, and actuated by a driving cam, and with a pressure spring for the suction stroke bearing against the inner face-of. the piston.

In this known piston pump the pressure spring only controls the pistonbut not at the same time the suction valve consisting of a loose ball between the piston heads, so that this valve is left to itself and therefore operates irregularly. During the suction stroke the loose suctionvalve is subjected to continually increasing retardation forces which cause the premature closing of the suction passage so that the charge is throttled even during the suction stroke. This results in a very imperfect filling of the pump cylinder which considerably reduces the output of the pump. Owing to the uncontrolled suctionvalve this piston pump fails entirely especially in the case of high speeds of rotation or high speed pumps. The loose suction valve therein commences to vibrate relatively to the piston and opens and closes so irregularly that un-. avoidable disturbances occur and prevent the perfect running of the high speed pump. All these objections are so serious that high outputs cannot be obtained with piston pumps of this type.

The invention overcomes these objections and is characterized chiefly by a pressure spring continually acting on the suction valve and on the other hand acting on the piston only during the flow.

An embodiment of the invention is illustrated by way of example in the accompanying drawing, in which:

Fig. 1 shows a pump in section on line A--A of Fig. 2,

Fig. 2 is a section on line BB of Fig. 1,

Figs. 3 and 4 show details .on a larger scale.

a is a crank case with cam shaft b, suction pipe 0 and driving cams d. The lifted liquid, for example oil, flows from the suction pipe 0 through holes e into the cam chamber which it fills entirely.

In each of two cylinders f a cup-shaped piston y, It is aicially shiftable and accommodates in its lower part 9 a suction valve h, 2' whose disc it forms the piston head adjacent the drive. The upper part lc of the cup-shaped piston has an internal diameter larger than the diameter of the spindle h of the suction valve and forms a shoulder m acting as inner surface of the piston head and which, when the suction valve h, i

is closed, lies below the end face n of the valve spindle h. The suction valve 72, Ms controlled by a pressure spring 0. spring bears against the end face 71 of the valve spindle h acting as spring abutment plate and its upper end bears against an abutment p on the upper end of the cylinder. The pressure spring 0 is so constructed and its windings are so dimensioned that its lower end bears continually against the plate n of the valve spindle h but can bear against the inner shoulder m of the piston when the valve has been pushed down. I

The pressureconduit s is connected to the chamber of the pressure valve 1'; t is the inflow passage in'the lower part g of the piston.

Fig. 4 shows a construction with a separate interposed spring abutment plate 11. which is so large that it also can engage on the shoulder m of the piston.

The operation is as follows:

In the position shown in Fig. 2 and in the left piston of Fig. 1 the suction valve h, 2' is closed and the pressure spring 0 acts only onthe suction valve. When the pump is started, the driving cam 01 gradually liberates the valve disc 2 as the eccentric stroke becomes less, with the result that the spring-contro1led suction valve h, 1 opens up to the valve stroke (Fig. 3). In this position the pressure spring 0 begins to act upon the inner shoulder m of the piston, so that then the opened valve 11., i and the piston g, h are controlled by this spring. Owing to friction the piston remains at rest during the opening movement of the suction valve and is moved alon only when the pressure spring 0 begins to act on the inner shoulder m of the piston so that from this moment both the suction valve and the piston are jointly controlled and shifted by the pressure spring 0. The ring-shaped part of the inflow passage t consequently remains constantly open, so that the pump cylinder is uniformly filled and without loss during the entire suction stroke. Shortly before the end of the suction stroke (Fig. 1 right hand piston) the piston automatically closes the inflow passage t in that the piston-owing to its inertia and the retardation occurring in the last portion of the cam movementmoves away from the pressure spring 0' and moves into contact with the valve plate 2'. During the closing of the suction valve the driving cam has reached its lower dead centre position and the pressure stroke of the pump commences during which the pressure spring 0 bears only on the spring supporting plate 12, that is only acts on the suction valve h, i, and gradu- The lower end of the ally extends until the initial position is reached.

As the suction valve and piston are controlled continually by the pressure spring during the suction stroke a perfect filling is attained, so

that the suction stroke is utilized for the fillin completely free from loss, or practically nothing or the filling is lost and the pump operates at full capacity. The speed of rotation of the pump is immaterial; even in the case of high-speed pumps the suction valve and piston operate free from disturbances.

Ihe counter-flowing liquid exerts a cushioning effect during the closing of the suction valve, with the result that hard knocks are avoided and a smooth running of the pump is ensured and the valve and piston are saved. Owing to the favourable degree of efliciency the very simple an inner shoulder in said cup-shaped piston at the upper end of said axial bore, a suction valve in said bore, an eccentric cooperating with said suction valve to reciprocate said piston in said cylinder, and a helical spring in said cylinder constantly acting with its lower end on said suction valve and on said inner shoulder in said piston only when said suction valve has been opened.

2. A piston pump as specified in claim 1, in which the suction valve has a valve disc forming a head of the piston and in permanent contact with the cam.

3. A piston pump as specified in claim 1, in which the shoulder forms an abutment for the spring during the suction stroke of the piston.

4. A piston pump as specified in claim 1, in which the inner shoulder and the pressure spring are of such a diameter that the spring bears permanently on the suction valve and comes into contact with said shoulder during the suction stroke.

5. A piston pump as specified in claim 1, in which a plate is introduced between the end of the spring and the suction valve, said plate being of such diameter that it bears against said shoulder under the action of said spring during the suction stroke of the pump.

MAX ROEDEL. 

